Inner layer of chorionic villi

Syncytiotrophoblast

outer layer of chorionic villi

Trophoblastic layer of cells in the blastocyst is basically what?

Placental stem cells

Implantation takes place on what day

6-7

hCG is a product of

the placenta and more specifically, trophoblast cells

7

What is the system responsible for the rolling of the blastocyst along the endometrium prior to implantation?

L-selectin system

8

Describe the L-selecting system

ok...SO the blastocyst expresses the L-selectin- this allows the blastocyst to weakly interact with the glycocalyx which lines the endometrial surfaceand then BOOM----- hCG is secreted by the trophoblast cells of the blastocyst

9

What does hCG do to the endometrium

It stimulates the upregulation of TROPHININ on endometrial epithelial cells. This trophinin contain pnipodes. The blastocyst then strongly binds to the endometrial surface via the trophonin trophonin binding.

10

So hCG

stimulates the growth of pinopodia on the endometrium

11

What is decidualisation?

It is the increase in vascular permeability and secretory activity of stromal cells in the endometrium. It really is the response of the maternal cells to progesterone

12

What stimulates decidualisation?

Attachment....this hCG initiate process

13

LIF and EGF

signals that come from the endometrial stromal cells

14

KNOW

Decidual reaction occurs in very early pregnancy. Appears in the area where the blastocyst contacts teh endometrial decidua. Consists of an increase in secretory functions of the endometrium.

15

Invasion

- Within hours of attachment trophoblasts destroy epithelial cells- Some trophoblast cells fuse and become syncytiotrophoblast- Other trophoblast cells retain their cellularity (cytotrophoblasts)- Finger like outgrowths called villi invade the decidua and attack blood vessels- The villi are then invaded by embryonic blood vessels

When does this invasion occur>

first 2-3 weeks of gestation

Describe the syncytiotrophoblast

So, realize that the chorionic villi is made up of the syncytiotrophoblast and the cytotrophoblast.

The chorionic villi is what invades the decidua

19

The arrangement of embryo surrounded by cytotrophoblast, syncytiotrophoblast, and maternal tissue remains the paradigm throughout gestation

ok

20

Remember, what is the most important job of the syncytiotrophoblast

secretes hCG which stimulates the corpus luteum to make progesterone during the first trimester

21

At what point during gestation is a vascular network established in the placenta with facilitates maternal-embryonic exchanges of gases, nutrients, and metabolic waste products

end of fourth week

22

secondary chorionic villi>

Early in the third week of gestation, mesenchymal tissue invades the primary chorionic villi and this forms secondary chorionic villi

23

Secondary chorionic villi cover....

the entire chorionic sac

24

chorionic villi cover the entire chorionic sac until when>

week 8 when the villi begin to be compressed. This reduces the blood supply to the villi and eventually the degenerate producing a relatively avascular area

25

What is this avascular area which succeedes the chorionic villi called?

smooth chorion

26

KNOW: Spiral arteries do not have a muscular layer which makes them very low resistance. You must have a ton of blood going to the fetus in order to make it develop, you need very low resistance vessels

In order to make make the spiral arteries good enough for this task, they must be remodeled.

27

What are the two mechanisms of spiral artery remodelling?

- interstitial - intravascularKNOW

28

Pre-eclampsia is caused by

faulty trophoblast invasion during pregnancy. Leads to high resistance in the spiral arteries and can cause IUGR